84 PRINCIPLES OF STOCK-BREEDING. 



the food required for its support. The celebrated 

 naturalist, Milne-Edwards, in his article on Crustacea, 

 says, " It has long been admitted as an axiom in ani- 

 mal physics that, when any particular part of the body 

 acquires a very high degree of development, certain 

 other parts stop short of their ordinary state of evolu- 

 tion, as if the former had obtained their unusual incre- 

 ment at the cost of the latter." 1 



Cuvier, the great comparative anatomist, claimed 

 that "all organized beings, in their structure, form 

 a complete system, of which the parts mutually cor- 

 respond and conduce to the same definite action by a 

 reciprocal reaction. Each of these parts cannot be 

 changed without the others changing also; and, by 

 consequence, each of these taken separately indicates 

 and gives all the rest." a 



Prof. Owen, in his valuable work on the " Com- 

 parative Anatomy of the Vertebrates," gives the fol- 

 lowing illustrations of this law of development : " As 

 vertebrates rise in the scale, and the adaptive principle 

 predominates, the law of correlation, as enunciated by 

 Cuvier, becomes more operative. In the jaws of the 

 lion, e. g., there are large laniaries, or canines, formed 

 to pierce, lacerate, and retain its prey. . . . There are 

 also compressed, trenchant, flesh-cutting teeth, which, 

 play upon each other like scissor-blades in the move- 

 ment of the lower upon the upper jaw. The lower 

 jaw is short and strong ; it articulates to the skull by a 

 transversely-extended convexity, or condyle, received 



1 " Cyclopaedia of Anatomy and Physiology," vol. i., p. 757. 

 9 As quoted by Prof. Owen, " Comparative Anatomy of the Verte- 

 brates," vol. i., p. 27. 



